U.S. Pat. No. 5,482,910 describes a catalyst preparation method that involves using a chelating ligand such as EDTA. An aqueous solution comprising the chelating ligand and a salt of an alkaline or alkaline-earth metal is first prepared at a temperature ranging from about 80° C. to the boiling point temperature thereof. This solution is then mixed with a solution comprising a group VIII metal. This solution is aged at a temperature ranging between about 40° C. and 100° C., then it is used for impregnating the support. The impregnated support is thereafter dried, calcined, optionally oxychlorinated and finally reduced.
U.S. Pat. No. 3,259,589 describes a catalyst preparation method comprising preferably platinum preferably deposited on an alumina. The platinum can be introduced in complexed form by an organic acid of HOOC[CRR′]n COOH type, with R═OH, H or an alkyl function and R′=H, an alkyl function or COOH.
U.S. Pat. No. 2,889,287 describes a hydrocracking catalyst preparation method comprising at least one active metal selected from the group consisting of groups VI and VIII metals of the periodic table and the oxides of said metals, a support selected from the group consisting of alumina and silica-alumina. The active metal(s) is (are) deposited on the support by impregnation of the support with a complex of the metal(s), then the impregnated support is dried and calcined.